Grinding wheel truing apparatus



vMarch 7, 1939. c: c. ALvoRD GRINDING WHEEL TRUING APPARATUS Filed March l5, 1957 2 Sheets-Sheet l EHHRLES E. HLVURD March 7, 1939. C. C. ALVORD 2,150,091l

GRINDING WHEEL TRUING APPARATUS Filed March 15, 1937 v2 Sheets-Sheet 2 Fig 8 3mm,

HHRLES E. ELL/URD Panarea Mar. '1,1939A UNITED STATES ammi WHEEL TBUING APPARATUS Charles (2.-Alvord, Worcester, Mass., asslgnor `to Norton Gompany, Worcester; Mass., a corporaltion o! Massen Application March 15, 1937, semi' No. 130,863

13 Claims.

The invention relates to grinding machines, and more particularly to a truing apparatus for truing a. plurality of spaced grinding wheels.

One object ofthe invention is to provide a'simple, thoroughly practical truing apparatus for truing a predetermined form on a grinding element. Another obiect of the invention is to true a plurality of spaced cylindrical portions oi different diameters on a grinding element. Anm other object of the invention isto provide an improved truing apparatus whereby a single truing tool is varranged. to true a. plurality of spaced grinding wheels in a multiple wheel grinding machine. Another object of the invention is to proi5 vide a trning apparatus for a' multiple wheel grinding machine, ir. wmch a single trning `vtool is traversed across t. e faces of a plurality oi wheels to trae the seme to predetermined relative diameters. A. further object of the invention is to provide an improved hydraulically operated multiple wheel truing apparatus. A further object of the invention is to provide a power reciprocated, cam controlled truing tool which is arranged for movement in a path successively to true either form on the periphery of a. single grinding wheel or to true a plurality or" grinding wheels of dierent diameters. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the icatures of construction, combinations oi. elements, and arrangements of parts, as will be exempliiied in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is shown one of various possible embodiments of the mechanical features of this invention,

Fig. 1 is a iront' elevation of the improved truing apparatus mounted on the wheel slide, having the wheel guard removed; V

Fig. 2 is a right-hand end elevation, partly in section, taken approximately on the line 2 2 of Fig.' 1, showing the horizontal` slide and parts in section and the remaining-parts of the mecha.- nism in elevation; Y Y, Fig. 3 is a. horizontal sectional view, takenA a proximately on the line 3 -3 ci Fig. 1, after showing the other parts of the mechanism inV pian vlew;

ratus, having parts of the main frame broken away and showr in section, together with a, piping diagram of the hydraulic system;

Fig. 5 is a. fragmentary front elevation, on an Fig. 4 is a rear elevationV of the trulng appaenlarged.. scale, of the latch and trip mechanism Vfor the main control valve;

Fig. 6 is a. fragmentary view, showing fragments of the grinding wheels and showing in dotted line the path of the truing tool across the wheel;

Fig. 'i is a detail view of the enlarged scale; 7

Fig. 8 is a fragmentary view, onan enlarged scale, of a. portion of a modified cam;

Fig. 9 is a. fragmentary view, showing fragments of the grinding wheels and showing in dotted line the path of thetrung tool in accordance' with the com shown in Rg. 8; and

Fig. 19 is a. iragrlentary view, showing a portion of a single grinding wheel and showing in 4dotted line the path of the truing tool across the wheel.

The improved truing apparatus has been illustrated in the drawings as mounted xedly on top of a wheel slide lil which rotatably "supports a. wheel spindle li carrying a plurality of spaced grinding wheels l2 and i3 of different sizes or diameters. i 'l The wheel slide l@ s pports a frame or base le of the truing apparatus. An adjustable horizoncontrol cam, on an tally arranged member is is pivotally connected by a. stud it with the frame itl.V An adjusting screw il threaded into a lug ii! projecting from the oase i4 serves to adjust the member l5 about its stud or pivot it to facilitate adjustment oi the position of the member l5 relative to the base. A lock nut lserves to lock the screw l1 in adjusted position. The member l5 may be clamped in adjusted position on the frame i4 by means of clamping screws 25 which pass through elongated slots 26 in the lugs 21 on the frame Hand are screw threaded into the member l5. A dovei tailed slideway 2B is formed integral with the member Hiand is arranged to support a horizontally movable slide 2 i having a dovetailed surface 22 which mates with the dovetailed slideway 20.

the dovetailedways J2li and 2l, servesto take up lost motion between the xed and movable parts of the slide. Ascrew 24 is provided to facilitate endwise adjustment of the gib.

y Ap adjustable tapered gib 23, interposed between The horizontal 'slide 2l is provided with a vertically arranged member 28 which is formed integral therewith or xed thereto. The vertically extending portion 28 of the horizontal slide 2l is provided with a dovetailed Aslideway 29 which sup-y ports a. vertically movable slide 30 having a. mating dovetailed way 3|.` serves to take un lost motion between the dove- An adjustable tapered gib 32 2 tailed slideways 26 and 3|, and a screw ,33' serves to facilitate adjustment of the gib az.

. ranged so that it may be moved vertically during the horizontal-movement ofj` the horizontal slide 2|. Y

The vertical slide 36 adjustably supports a truing tool holder which in the present case is formed as a cylindrical bar 46 which slidably is keyed in an aperture 4I formed in a projection 42 .of the slide 36. The truing tool holder or bar 46 is arranged to be clamped in adjusted position within the aperture 4I in the projection 42 of the slide 36 by binding screws 43 and 44. The truing tool Asupport 46 carries at its outer end a truing tool 45 having a diamond point 46 arranged for successively truing the peripheral surfaces of the grinding wheels I2 and I3.

The slide 35 is preferably adjustably connected to the slide 36 so that during the traversing movement of the horizontal slide/2|, the vertical slides 36 and 35 are moved together in a vertical direction to control the path of movement of the l diamond or truing tool 46. The slide is provided with a forwardly extending boss or lug 50. A vertically extending feed screw 5| is rotatably connected to the lug 56 and extends downwardly through a nut 52 carried by or formed integral with the vertically arranged slide 36. The lower end of the feed screw 5I is journaled in a suitable bearing 53 formed .within a casing 54 which is integral with the vertical 56. A worm gear 55 is ixedly mounted on the lower end of the feed screw 5I. The worm gear 55 meshes with a worm 56 formed on the inner end of-a rotatable shaft 51. The shaft 511s journaled in bearings (not -shown) within the casing 54 and is provided at movable slide '2| to traverse the truing tool 46 relative to the periphery of vthe 'grinding wheels I 2 and I3. In the preferred form, a uid pressure "traversing or reciprocating mechanism is proother end of which is fastened. by nuts 63 to an vided comprising a cylinder 66 which is formed within the member I5. A slidably mounted piston 6| is mounted within the cylinder 66 and is connected to one end of a piston rod 62, the

end cap 64 formed integral with or -iiredlyV mounted on the end of the horizontal slide 2|.' As nuid under pressure is admitted either through a passage 65 into a cylinder chamber 66 within the cylinder 66, or through a passage 61 into a cylinder chamber 66 within the cylinder 06,' the piston is moved longitudinallyto traverse .or reciprocate the horizontally arranged slide 2| to traversethe truing tool 46 across the face of the grinding wheels IIand I3.-- l

The admission of fluid under pressure to the cylinder chambers 66 and 66 is preferably controlled by a control valve 66 which in the. present case is a rota'ry type valve. Fluid under pressurer from a suitable source', such mi a fluid pressure [pump (not shown), either -withinpthebase' 0rv f/audaci s contrai valve ss, and through thee s1 into the cylinder chamber 66 to causethe piston 6| and the slide 2| together with the truing tool 46 to move toward the right (Fig. 4). During the movement of the piston 6| toward the right (Fig. 4), uid within the ,cylinder chamber`66 exhausts through the passage 65 and a valve chamber 12 and through a pipe 13 and a pipe 14 into a reservoir (not shown) within the baseA of the machine. 'A speed control valve 15 is interposed between the pipes 13 and'14. The valve 15 isy preferably a balanced piston type valve which is supported by a bracket 16 projecting'upwardly from the member I5. The valve 15, in the position illustrated in Fig. 3, 'allows unrestricted passage of uid from pipe 13 into exhaust pipe 14 to allow the piston 6I and the horizontal slide 2| to move at a comparatively fast rate during the idle stroke of the slide.

During the truing operation. that is during the slide 2| and the truing tool 46 to a very slowl uniform speed for the truing operation. This is preferably accomplished by providing a cam bar 66 which is fastened to the slide 2| by screws 6I and 62. Elongated slotsy 63 'and 64 in the cam bar 66 serve to facilitate a longitudlnaladjustment of the cam 66 relative to the stem of the valve 15. 'I'he cam 66 is-preferably so shaped that when the truing tool 46 engages the periphery of a grinding wheel, the valve is moved for-- Ward by a spring 65so as .to maintain a follower 66 onvthe valve -stern in operative contact with the cam 66. When the truing tool 46 is about to engage the grinding wheel, the follower moves forwardly to close the valve 'I5 and thereby to prevent .further passage of'iluid therethrough. After the valve 15 is closed,vuid under pressure is by-passed through a throttle or needle valve 61 (Fig. 4) the adjustment of which lserves to produce the desired slow traversing movement of the truing tool.

The cam bar 66 is preferably so shaped that the valve 15 will be so controlled that-the truing tool 46 and its supporting slide 2-I will be moved at a rapid rate until the truing tool engages the grinding wheels |2 or I3, after which a slow traverse will be. obtained until the truing tool 46 passes entirely 'across the face thereof, after which a projection on the cam 66 serves again to open the valve 15 to speed up the movement of the slide 2| and the truing tool 46 during the idle stroke between the two wheels after slowing down the movement of d thereslide.2I

and truingtcol 46 to a truing speed as the truing' tool 46 engages the periphery of the second -wheel to true the same. By means of the valve control eration is reduced to a minimum.

In` truing a` grinding wheel. it is desirable to above described, the idle time of the truing opeach truing operation. For manytruing opertrated for controlling the valve 66 so that the truing tool 46 makes one complete reciprocatory stroke and then stops. A manuallyf operable handle or knob '66 is xed to the rotary part of the valve 66 and may be rotated in a eounterclocklreciprocate the truing tool across the surface of the wheel either one or more reciprocations for ations, a single ycomplete reciprocationis sufficient theseconcentric portions A and Cfare provided i on the cam4 |00, each surface beingarranged to..

in a plate 93 supported by the rotary part of the valve 69. This movement of the valve starts the traversingmovement of the slide 2|v and the truing tool l0 toward the left (Fig. 1) to pass the truing tool across the faces of the wheels yI2 and I3. The traversing movement of the tool 4 6 and slide 2| toward the left (Fig. 1) continues until an adjustablypositioned collar or dog 94 on a rodl 95 carried by the slide 2| engag a cam surface 96 on the spring actuated pawl |,thereby with,- drawing the pawl 9| from engagement withythe notch 92. A weight 01 carried at the end of ,a'

lever 98 operating under the influence of gravity rocks the valve 69 in a clockwise direction (Figs. 1 and 5) to reverse'the vposition of the valve and thereby reverse the movement of fluid within the system to reverse the movement of the truing tool I6 and the slide 2| to traverse the same in the revers'e direction across the peripheral faces of the wheels i3 and l2, respectively. When the piston engages the end of the cylinder in its movement toward the right (Fig. 1), the truing tool 4S stops and remains in this position, when the grinding operation isresumed.

In order that 'the truing tool 46 may true a plurality of spaced grinding wheels of different diameters, such as a pair of spaced wheels l2 and it, respectively, it is desirable to provide .a suitable control mechanism to move the slides and vertically in timed relationship with the traversing or reciprocating movement of the slide 2i so that a single truing tool 46 may be utized to true both wheels, that is so that the ydiamond may pass across the-peripheryl of the wheel i2 and then the slides 30 and 3 5 may be moved into' a second position to true the periphery of the wheel i3. Due to the short space between the A two grinding wheels and due to the difference in their diameters, it is not feasible to utilize a xed cam bar for this purpose. To overcome this dimcnlty, a rotatable cam itil is preferably utilized to transmit a vertical motion -to the-slides til and 35, which movement is controlled by the longitudinal traversing movement of `the truing tool it and the horizontal slide 2 i The rotatable cam lilo is supported on a shaft |0l which is supported on the vertical member 28 which is integral with the horizontal slide 2i. The outer end of the shaft illi is supported in a bearing li formed integral with a bracket m3 which straddles the slide 35 and is ilsedly mounted to the vertical member 28. on the vertically movable slide 35 and is arranged to engage the periphery of the rotatable cam itt, ln order to transmit the desired vertical movement to the truing tool 4B and its supporting slides in timed relation with the traversing movement of the horizontal slide 2 l, a rack bar i05 is xedly mounted on the member i5. A gear 05, either formed integral with or connectedto rotate with the cam |00, meshes with the rack |05 and transmits a rotary motion to the cam |00 as the shaft supporting the cam is moved longitudinally durihg the traversing movement lof the slide 2| and the truing tool 45. The cam |00 is provided with portions A and C (Fig. 7) which are concentric with its axis of rotation so that when the diamond or truing tool 46 is in engagement with the wheels, the vertical slides 35 and 30 `will be held stationary so as to permit the truing tool 46 to move in a. straight-line path to produce a true cylindrical surface on the periphery of the wheels', l Two of A follower |0ii is xedly mounted position the truing tool for truing the respective "'slide abruptly from one diameter to that the cam |00 be so I lized to vproduce the surfaces of the two wheels. The rises and'mi D of the cam IIIQ/(Flg'Jl) between the two concentric surfacesfserves It from one position to the other and, due to the fact that vva rotary movement of the cam Ill is speeded/up during the idle stroke ofthe slide 2| and truing tool IB between the wheels there is no difficulty experienced in raising the true a wheel vof a larger diameter, or viceversa.

In truing a plurality oo f grinding wheels, such 'as wheels l2 and I3, each having a true cylindrical surface to be trued, it is desirable that the contour or shape of the cam |00 be such that the operative cutting point of the truingtool 46 be moved in the same path when traversed in each direction. In lorder to avoid thev possibility of lost motion in the slides or parts affecting the positioning of the truing tool I6, it is desirable' designed (Fig. 8) that the slides 30 and 35 always move downwardly into a definite locating position Ywhen the concentric portions of the cams rotate into engagement with the' follower, thereby laccurately locating the diamond or truing tool v'4t in the same identical position on each pass .of the truing tool. To accomplish this result, it is desirable to lift the truing tool supporting slides 3@ so that the tool 48 is raised slightly above the' path of. travel across the large diameter wheel. .asillustrated ,in Fig. 8, a high point iit is provided at each end of the concentric portion C of the earn |00, so that A"when the diamond or truing tool 5f approaches the position for the larger diameter i2, the truing tool dt and slides 3i? and 35 slightly above its truing position and then allotted to drop onto t e cone-entric portion C. The truing tool at is thereby moved into the identical position as it engages the wheel in its path of movement in either direction, 'thus insuring a precisevtruing or 'the wheel face when the truing tool it is moved in either direction. Similarly, the end of the travei of the diamond toward the left (Figs. i and 9) the diamond is raised to a position slightly above the path of travel across the wheel it so that when the traversing movement of the siicle gli and the truing tool is started in the reverse direction, the truing tool itt the slides :it and 35 are lowered to bring the truing tool into position fortruing'the wheel iii as it in a direction toward the right (Fig. l). L f desired, the truing inay be utifor truing a predetermined forni or consingle grinding wheel (Fig. lil). In such acaso, the truing tool it is traversed across the peripheral face of a grinding wheel iiin the manner above described. The cam itil (Fig. 7) :is rotated by and in timed relation with the traversing movement of the slide :2l to cause a vertical movement of' the truing tool towarcl or from the operative face of the grinding wheel H5 to produce a predetermined contour thereon. A predetermined torni or contour may be produced on the periphery of a single grinding Wheel by -provhiirig acari: it@ which is shaped desired form. preferably mounted se that it may be readily removed and replaced with a cam of a different shape when it is desired to true a grinding wheel or grinding wheels to a different shape or size.

if desired, thetruing apparatus may be utitour on a tocarrythetruingtool" I2 and I3.

Ehe cam |00 is lized for truing a single grinding wheel to a slides 30 and 35 are raised a sumcient distance to move the follower |04 fout of engagement with vthe cam |00, and the slide 35 is then locked in adjusted position by clamping screws |08 and |09 which pass through elongated slots Il 0-and III in the'vertically extending member 28 and are screw threaded into lugs H2 and III which project from the sides of the slide 35, thus locking `the vertical slide so that thegltruingvtool may be traversedbymeans'f the piston and gcylinder'mechanism above described. The truing tool may be adjusted relatively toward and from the wheel to be trued by rotation of the feed wheel 58 which slides through 4the rotatable screw 5l and the nut 52 to adjust the position of the slide 30 relative to the slide 35. i

The operation of this truing appar-atm will be readily apparent from the foregoing disclosure. Assuming the cam I is mounted in place on the shaft |0I, and the truing tool is adjusted into its proper position, the manually operable wheel 50 is rotated to cause a downward movement of the slide 30,relative to the slide v35 to position -the truing tool 46 for a truing operation. 'I'he knob 90 is then turned in a counterclockwise direction (Figs. l and 3) which serves to move the arm 98 and weight 91 in a counterclockwise direction (Figs. 1 and 3) so as to .posi tion the rotary part of the valve 69 in the position illustrated in Fig. 4. In this position of the parts, the pawl 9i drops into the notch 92 rand holds the valve 69 in this position while the truing tool 46 traverses from a right-hand position 46a, as shown in dotted lines in Fig. 1, toward the left 'into full line position 40. As the truing tool approaches" the full line position (Fig. l), a collar or dog 94 engages the cam 90 to rock the pawl 9| out of engagement with the notch '92, and the influence of gravity on the weight91 and the arm 90 serves to reverse the position of the valve 69 toreverse the ow of fluid within the fluid pressure system so as to traverse the truing tool ltoward the right (Fig. 1). The movement'of thetruing tooltoward the right `continues until the piston 0 I engages the end of the cylinder 60 and the mechanism then stops in this position. A second reciprocation of the truing tool may be had,

' ,if desired, by again turning the` knob 90 .to shift the yalve and start a second reciprocation; By adjusting the wheel 50,.l the desired amount may be trued from the periphery lof'the wheel.

It will thus be seen' that there has been provided by this invention apparatus in which the variousv objects hereinaboveset forth together with many thoroughly practical advantagesfare" successfullyachieved.Y many possible em- Y -bodimen'ts' may be made of the abovevinvention truing tool across the and as many changesmight be made in' the embodiment above set forth, it is to be understoodl that all matter hereinbefore `set forth or shown in the accompanying drawings is .to be interpreted as illustrativejand not in a limiting sense.

I claim:

1. In a grinding wheel truing apparatus, a truing m01, a 1ongitudina11y traversame mail; tool holder, means togtraverse said holder 'and Vperipheral face of a g/rinding wheel, and means including a rotatable cam and follower which are actuated by and in timed relation with vthe traversing movement of said holder and -tool to mo've the tool toward and from the periphery ofthe grinding wheel to true `a predetermined shape thereon.

2. In agrinding wheel truing apparatus, a

allumer truing tool across the peripheral face of a grinding wheel, means including a rotatable cam and a follower which are traversable with said holder and tool, and means actuated by and in timed relation with the tmjLeLsingfmovement/f"said .Q Qlderwand-tool't rotate said cam to move the Vtool toward and from the periphery of the grinding wheel to true a predetermined shape thereon.

3. In a. grinding -Wheel truing apparatus, a truing tool, a longitudinally traversable truing tool holder, means to traverse said holder andv truing tool across the peripheral faces of a plurality of grinding Wheels of different diameters. means including a rotatable cam and a follower which are traversable'with said holder to move said tool transversely toward and from the peripheries of said grinding wheels, and means actuated by and in timed relation with the longitudinal movement of said tool to rotate said truing tool across the peripheral 'faces of a plurality of grinding wheels of different diameters,l means including a rotatable cam and a follower to move said tool transversely toward and from the peripheries of the grinding wheels, and means including a rack and gear mechanism actuated in timed relation with the longitudinal movement ofssaid tool to rotate said cam and follower successively to position the tool` forltruing the grinding wheels of different diameters. I Y.,

5. In a. grinding wheel truing. apparatus, a truing tool, a truing tool holder, a vertically movable slide therefor, a horizontal longitudinally movable slide which supports said verticalslide, means to reciprocate said'horizontal slide so as to rtraverse lthe truing tool successively across the peripheral faces of a plurality of spaced grinding wheels 'of different diameters, means includingn a rotatable cam on said horizontal slide-and a follower on said vertical slide to move said'slide ary rack-to rotate Asaid gear and cam by and in,V Y.

theVv movement of YsaidY horltim`ed relation with zozrtal slidefV i Y A V6. "In a grinding wheel truingapparatus, a truing tool, a truing tool holder, means to adjust the holder and tool relative to the vertical slide, a vertically movable slide therefor, a horizontal longitudinally movable slide which supports said vertical slide, means to reciprocate said horizontal slide so as to traverse the truing tool successively l across the peripheral faces of a plurality of spaced grinding wheels of different diameters; means including a rotatable cam and a follower to move said slide vertically -to position the truing tool in operative f relationV with successive grinding wheels, and means including a rack and gear mechanismto rotate said cam Vby and in timed relation with the movement of said horizontal slide. Y

7. In a grinding wheel truing apparatus, a truin'g` tool, a vertically/movable slide therefor, a. horizontal longitudinally movable slide vwhich supports saidwertical slide, auid pressure mechvalve to controlthe admission of uid to either i anismincluding a piston and cylinder operatively connected to reciprocate the horizontal slide so as to traverse the truingvtool successivelyr across the peripheral faces of a plurality of spaced grinding wheels of different diameters, means. including a rotatable cam and a follower oneofwhich is on the horizontal, and thel other of which is on the vertical slide to move said slide vertically to position the truing tool in operative relation with successive grinding wheels, and means including a rack and `gear mechanism which are actuated by the horizontal slide to' rotate said cam.

l 8. In a grinding wheel truing apparatus, a truing tool, a vertically movable slide therefor, a horizontal longitudinally movable slidef whih supports said vertical slide, a fluid pressure mech-A anism' including a piston and cylinder operatively connected to reciprocate the horizontal slide so as to traverse. the truing tool successively across the peripheral faces of a plurality of spaced grinding wheels of different diameters, means including arotatable cam and a follower to move said slide vertically to position the truing tool in operative relation. with successive grinding wheels, means lincluding-a rack and g\ ar'mechanism which are actuated by the horizontal slide. to rotate said cam, and a control valve mechanism for -said fluid pressure mechanism' to traverse the truing tool slowly when in engagement with the wheels and rapidly when out of engagement therewith. i y 9. Ina grinding wheel truing apparatus, a truing tool, a truing tool holder, means' to adjust the position ofsaid holder and tool relative to said vertical slidefa vertically movable slide therefor, a horizontal longitudinally movable slide which supports. said vertical slide, means including a piston and cylinder to reciprocate said horizontal slide so as to traverse the truing tool successively across vthe peripheral faces f a plurality of spaced grinding wheels of different diameters, means pass valve associated therewithwhich-.are ar ranged to cause a rapid movement of said slide 10. In a grinding wheel truing apparatus,` a truing tool, a. truing tool holder, a vertically movable across the peripheral faces of a plurality of spaced grindingrwheels of' dinerent'dlameters, means including a rotatable cam and a. follower` L `to move said vertical slide and posi-tion the truing o cessive grinding wheels, means incl and gear operatively connected to rotate said cam tool successively'in operative position with suc- `a. rack when, the' slide is traversed. a reversing end of'said cylinder, a speed control valve to control the speedV of -movement of said tool, and a. cam arranged to actuate said speed control valve so as to cause a. rapid movement of said slide and 5 tool when the tool is out of contact with the grinding wheels and to cause a slow uniformv movement thereof when the tool is traversing' across the face of the grinding wheels.

11. In a grinding wheel truing apparatus, a 10 said vertical slide, manual means to adjust said 15 holder vertically relative to said vertical slide, a truing tool thereon, means including a piston and cylinder to reciprocate said first slide longitudinally to traverse the truing tool across/'the-pe'- ripheral faces of a plurality of spaced grinding 20 wheelsof different diameters, means including a rotatable cam and a. follower to move said vertical slide,'and means including a. rack and gear mechanism which are actuated in timed relation.

with the longitudinal movement of the rst slide w25 to rotate said cam and shift the position, of th vertical slide and truing tool.

i 12. In a grinding wheel truing apparatus, a frame, a longitudinally movable slide on said frame, a vertically' movable slide on said hori- 3o zontally movable slide, a truing tool holder on said vertical slide, atruing tool thereon, manual means to adjust said holder vertically relative to said vertic'al slide, means to reciprocate said irst slide to traverse the truing tool across the perlph- 35 eral faces of a plurality of spaced grinding wheels of diil'erent diameters, arotatable cam on said horizontal slide, a`follower on the vertical slide,

'a gear to rotate said cam, and a rack bar on'said ar and cam whenthe hori- 40 frame to rotatef said zontal slide is traversed.' Y

13. In a .grinding wheel truing apparatus a truing tool, a. truing tool holder therefor, means including a piston and cylinder to traverse said truing tool across the'face of a plurality of spaced 45 grinding wheels of different diameters, -means actuated' in timed relation' with the traversing movement of said tool tomove the tool transversely relative to said wheels successively to position the tool for truing the grinding wheels of 50' different diameters, a uid pressure control valve, a. weight normallyl to hold said valve in one position, manually operable means to move said valve to start the traversing movement of said holder, a

latch to hold said valveA in a traversing position, 55

a' speed control valve in said system, a cam to actuate said valve which is arranged to open said valve during the idle stroke ofthe truingtool as it approaches the operativefaces of the grinding wheels andbetween grinding wheels and is ar- 00 ranged Ato' close said `valve while the truing tool is in operative contact with the grinding wheels, and an adjustable by-pass valve rendered effective when the throttle valve is. closed to produce a slow uniform traversing movement of the tru- 05 ing ,tool across the faces or the-grinding wheels, and an adjustable dog which is movable 'longitu-` dinally with said truing-'tool holder to trip said latch after the h'olderhas traversed to a. predereverse the movement of said truing tool.A

GLAIIYCRD. 

